Vital signs of a person, for example the respiration rate serve as indicators for the current state of the person and as predictions of serious medical events. For this reasons, vital signs are extensively monitored in in-patient and out-patient care settings, at home or in further health, leisure or fitness settings.
Camera-based monitoring of the vital signs or physiological signals such as respiratory rate is a known technique for remotely or contactless measuring the vital signs of a person. The camera-based monitoring of vital signs allows apart from the advantage of being fully contactless, two-dimensional information, which enables a multi-spot and large area measurement, and often contains additional context information. This additional information can be used in the measurement of additional vital signs such as respiratory volume.
The respiratory volume measurement is important for respiratory disease diagnosis and therapy evaluation such as sleeping diagnosis and neonatology. Common systems for measuring a respiratory volume in clinical practice require the use of spirometers, however these spirometers are bulky, require a lot of probes and are flow-based measurements, which force the subject to breathe in and breathe out of a tube, which is extremely inconvenient for the user. The measurement is further highly dependent on the patient's cooperation and it interferes with the subject's normal respiration and the use is difficult for patients with breathing difficulties.
Existing camera-based respiration volume measurements require either the computation of a three-dimensional map of the entire thorax or need markers which are attached to the subject. The three-dimensional surface reconstruction requires an accurate estimation of the entire thorax by the camera and needs an active radiation source or multiple cameras to provide a reliable three-dimensional map which is a large technical effort. Alternatively, the use of markers, which have to be attached to the thorax of the subject is inconvenient in practice.
A corresponding apparatus for measuring the respiration variability using impedance contact probes for measuring the body movement is for example known from WO 2009 363 12 A2.
Other methods are known using depths-sensing cameras or three-dimensional cameras to detect the respiration and to determine the respiration volume of a subject.
The disadvantage of the known methods to measure the respiratory volume from a subject is that the technical effort is increased due to the complicated three-dimensional optical measurement of the respiration volume or that the use of the known systems is inconvenient due to the use of spirometers or markers for the detection of the motion of the subject's thorax.